Patent GB-975919-A (GB)
Title: Improvements in and relating to flying shears
Inventor: BAILEY JOHN SHACKLETON
IPC: B23D25/06
Filed: 1961-11-30
Abstract: 975,919. Shearing. LOEWY ENGINEERING CO. Ltd. Nov. 30, 1961, No. 42952/61. Heading B3W. A flying shear comprises two blades driven by a main reciprocating means from a rotating shaft, a miss-cut mechanism driven by the shaft and causing reciprocation of one of the blades, control means for putting the said mechanism out of action so that the main reciprocating means move the blades in a cutting cycle, and for putting the mechanism into action so that the main reciprocating means and the said mechanism together move the blades in paths spaced from one another. A base 10 has three spaced walls 11, 12, 13 supporting a main drive shaft 17, driven by a motor through an infinitely variable - speed gear - box. Formed on the shaft are two similar eccentrics 18, and keyed to it are two similar eccentric sleeves 19, the eccentricity of which is greater than that of the eccentrics 18 and approximately 155 degrees in advance thereof in the direction of rotation. A cutter frame 20 is supported on the eccentrics 19 and carries an upper blade 30. A lower blade 32 is bolted to a carrier 34 slidably mounted in the cutter frame and reciprocated therein by two follower straps 50, each mounted on one of the eccentries 18 and coupled to the carrier 34 by pivoted links 60. Rotation of the shaft 17 imparts reciprocating movement to the carrier 34 and rocking movement of the follower straps 50 about the eccentrics 18 will impart a supplementary reciprocating movement to the carrier. The cutter frame 20 is given a rocking movement about the eccentrics 19 by two follower straps 70 connected at one end to the frame by pins 89 and driven by a rocket shaft 71 which is driven by a variable throw crank disc 72 mounted on the shaft 17. The shaft 71 is connected to the crank disc by a rod 81 which is formed with a toothed rack 82 meshing with pinion 83 eccentrically mounted on, and keyed to the shaft 71. The two follower straps 70 are mounted on eccentric bearings 88 keyed to the rocker shaft 71. The supplementary reciprocating movement of the carrier 34 is produced by a further rocket shaft 95 mounted in bearings on the base 10 and coupled by levers 97 and links 98 to extensions of the follower straps 50. Angular movement of the shaft 95 will thus impart rocking movement to the follower straps 50 and hence reciprocating movement to the blade carrier 34. Clockwise movement of the levers 97 is limited by stop pads 100. Assuming that the throw of the crank disc 72 is zero, the cutting cycle of the shear is as follows. As the drive shaft 17 rotates the eccentrics 19 impart to the cutter frame 20 a vertical reciprocating movement and a rocking movement about the pins 89, which follow an arcuate path about the axis of the eccentrics 88, so that the upper cutter describes an elliptical path. The lower ends of the straps 50 follow an arcuate path about the axis of the pin connecting the levers 97 and 98 so that as the eccentrics 18 rotate the straps 50 have a combined vertical reciprocating movement and rocking movement and this produces reciprocating movement of the carrier within the frame 20, but since the carrier follows the rocking movement of the frame 20 the lower blade 32 follows an elliptical path which intersects'the lower section of the path of the upper blade. The mechanism comprising the crank disc 72, rocket shaft 71 and the follower straps 70 imparts to the frame 20 a rocking movement in order to synchronize the speed of the blades and the speed of the stock at the instant of cutting. With the stock running at constant speed the length cut is determined by the speed of the shaft 17, and with the shaft running at maximum speed the blades 30, 32 have a forward velocity equal to that of of the stock. As the shaft speed is reduced to increase the length cut the throw of the crankdisc 72 is increased to raise the speed of the blades at the instant of cutting. Miss-cut mechanism.-This comprises a follower strap 101 (Fig. 7) mounted on an eccentric 102 on the shaft 17 and connected to a main lever 103 which is mounted intermediate its ends on a pin 108. The other end of the main lever is connected by a link 105 to a lever 104 keyed to the rocker shaft 95. The pin 108 is mounted in a crank disc 106 which is secured to a shaft rotatable within a bearing in the wall 11. The disc 106 has peripheral teeth which mesh with a rack 12 contained in a guide 113 bolted to the wall 11. At one end of the guide is a plunger 120 connected to the piston of a single acting air-cylinder 123 and at the other end is a plunger 121 connected to the piston of a double-acting cylinder 125. During a cutting cycle pressure air is supplied to the right-hand end of the cylinders 123 and 125, so that the plunger 120 is held against the rack 112. As the shaft 17 rotates the eccentric 102 reciprocates the follower strap 101, and the main lever 103 pivots about the end connected to the link 105. The crank disc 106 oscillates to accommodate the movement of the pin 108, and the rack 112 moves against the thrust of the plunger 120. The thrust is transmitted to the rocker shaft 95 and holds the pad 97 on the stop 100. During a non-cutting cycle air is admitted to the lefthand end of the cylinder 125 at the instant when the follower strap 101 is at T.D.C. so that the plunger 121 follows the movement of the rack to the right as the shaft 17 rotates and as the strap 101 reaches B.D.C. the plunger 121 forces the rack a small additional amount and thereby rotates the shaft 95 anticlockwise and lifts the lever 97 off the pad 100. During the next halfrevolution of the shaft the thrust on the pin 108 is in a direction to hold the rack to the right and the valves controlling the cylinder 125 are operated to move the piston to the left. Reciprocating movement of the follower strap 101 with the rack and pin 108 stationary results in oscillating movement of the rocker shaft 95 which through the lever 97 and the link 98 imparts a rocking movement to the follower straps 50 which in turn reciprocates the carrier 34 in a direction opposite to the reciprocation produced by the eccentrics 18. The miss-cut mechanism thus reduces the amplitude of the vertical movement of the lower blade so that the blade paths do not intersect. In a modification the crank disc 106 is locked by a detent, operated by an air cylinder, to effect a miss-cut cycle, and in a further modification the pin 108 is mounted on a slide block movable in a guide bolted to the wall 11. During a cutting cycle the block reciprocates freely in the guide, and to effect a miss-cut cycle the block is moved to one end of the guideway by an air-cylinder unit.